318 Idle Issue
 

Hey guys, This is my first post and i would really appreciate some help. Been at this for about a week or 2 now.

So i just rebuilt my holley 4bbl and installed pertronix. My timing is all tuned in perfectly and my idle/mixture screws are good.

Problem: After about 1min of idle, the car will drop to about 4-500 RPM then slowly die off (Even if warm)

Also If i gas it mild-hard then let go, the car will have trouble picking back up and it will drop to very low rpm again and die almost instantly.

Any help please? Thanks alot. -Jayce

Note, i have also sprayed around the intake with carb claener. No sign of any vacumm leaks anywhere

J -

Are you using a choke?
Manual or auto and how was it set?

Archer

Automatic choke, i just did a little more tinkering and i felt some air coming out of the exhaust pipes right underneath the back seats, just before the muffler. Could an exhaust leak like that be causing it?

Could make you very sick/dead if you drive with the windows rolled up !!

J -

If there were air coming out before the muffler, you would HEAR it and wouldn't have to go looking to find or feel it. Or like TV said, you wouldn't be happy ...

Seriously a small exhaust leak can make you run lean, but usually not enough to cut the engine.

When the engine is dead cold, check the postion of the choke and check again after it's at full operating temp. If should be closed when cold and wide open when hot.

Other things to look at a lean fuel / air mixture and the coil. Some coils get cranky as they heat up and need replacing. Also make sure there are no wires arcing as the engine heats up.

Archer

sounds lean

wrong gaskets in carb?

Did you dip the carb or spray it ???

Archer, i will check the choke in the morning and look to replace my coil. Thanks.

moe7404 and TV, I was thinking it might need the thick intake gasket but i just matched up to the one it had on before. And the carb was dipped and the float levels are good

Could be EITHER rich and loading up, or lean

Where did you set timing? Have you done anything, even cursory, to check that the mechanical advance is working? Might be sticking

HOW did you set the idle and idle screws? You want to set the idle mixture so that the idle RPM or idle vacuum is peaked "off to the lean side" (CW on the screws)

Can you see or hear any fuel dripping into the throats? (high float level, bad floats/ needles, high pump pressure)

I have a couple question..... :)
Why did you rebuild your Holley?
Was it running bad or doing this before you rebuilt the carb?

But since you already got the carb rebuilt and back on the car... And got the Pertornix installed.

Check the carb Float's level's...
Check The fuel pump pressure...
Check the fuel filter for being Plugged or restricted.
Check to make sure the choke is fully opening, when warm...

Turn the idle air screws out 3 turns from all the way in as a starting point.
Try setting up the Curb Idle a bit higher.... Maybe 1 turn clockwise...

If you get to the point of it idling...Set the timing to about 12* BTDC..

And let see how that's working for now..... :)

Hi, the timing is set to 10* BTDC and no i haven't done anything to check the advance.

The idle screws are about 2 1/2 turns out. And i did actually see some fuel dripping down the throat the other day.. Fuel pressure is at about 7

Yeah the engine was running very ruff, bassically the same problems it is having now so my first bet was a clogged jet or a super low float level.

I cranked the mixture screws to about 3 out, and tightened up the idle screw. Timing is still at about 10*

The car is now sitting at 1k RPM, doesn't die out when i gas it (but gets close) and doesn't randomly die at idle

The Holley you have...... Do the bowls have sight glasses in them? If so Re-check the float levels....

No sight glasses

Take the bowls off and check the float adjustment...
Was anything done before it starting running bad??
How many miles on this motor?

Drove it home, 2 hour drive and it ran great. The next morning, it wouldn't idle in gear. then it just wouldn't idle. Then i got a PCV valve for it, and it ran great again, Then the problems returned. Motors got about 80k on it, not sure if flipped over or not. I will run through it and check everything tomorrow

I'm Thinking its got a bad timing chain that jumped time.....

But a few more checks before jumping into that.. :)

Carb definetly appears to be flooding. Fuel pressure bouncing around 8, and will backfire upon second fire up.

Back the fuel pressure down 2 PSI..... Pressure might be pushing threw the seats....

Just bought a regulator and a new vacuum advance for my dist. pretty sure the old was had a leak. Gunna throw those in and see how this goes

6 PSI is good

Well, the new vacuum advance is in... ALong with the regulator (which is set for 6psi). The PSi is at a steady 7 now. The fuel filter is not filling up with much fuel though...

Idle speed is fluctuating quite heavily from 8-1100 and when i gas it, it will stick at about 1400 RPM then slowly back down to 8-1100.. Timing is still set to about 10*, and i tuned the mixture screws down to 1 1/2 turn but the idle is still very high.

Again, i am stumped.. lol :doh:

You have a vacuum leak somewhere.....

Checked around the intake, where else are common places? All my hoses are good and i don't have a brake booster

Check the base gasket then....

Plug all the vacuum ports.....

J -

I have to ask this, where did you plug the vac advance into, it was a ported vac post, right?

Archer

Try and borrow a carb to try.. I think you still have carb problem. I would take it apart again and at least blow it out with some cleaner.. Holley ? Check the metering blocks for warpage

Archer, just a hose straight from the dist to a port on the side of the carb.

TV, i was sorta leaning at that.this wouldn't be the first time a carb has fooled me into thinking it was in the clear, then when i replace it the car runs good as new...

Just an update- Got the new 4barrel on it and as it turned out 2 of the plug wires were swapped. (The #2 and #4). The car drove around the block perfectly, everything sounded in tune and seemed good. Going to push it a little harder today, but so far it looks like the carb was just bad